cleaning contacts on the battery
looking at the contacts inside the battery compartment
cleaned the contacts on the lens and camera
tried a different memory card
tried powering up without a lens attached, or with a different lens

The blinking green light of death has hit my d90 and I need to know of there is anything I can do besides send it to Nikon, I am a very broke 17 year old and I'm worried about my camera Ahah I need all the help I can get!